1. Field of the Invention
The present invention relates to power controllers utilizing SCR controls with widely varying frequency of the power source.
2. Prior Art
Various SCR (Silicon controlled rectifier) types of power controllers have been advanced. Silicon control rectifiers are three lead semi-conductor devices with large power handling capabilities. SCR's are commonly used to control single or three phase power for inductive or resistive loads. An SCR is capable of providing current flow in only one direction, and has only two stages or states, on (or conducting) and off (or not conducting). An SCR has an anode, a cathode and a gate, and is capable of conduction from the anode to the cathode, only after it has been turned on by application of a suitable signal to its gate. After turn on, it will turn off only when the current through it is reduced to a value below what is called the "holding current". Normally the threshold value of holding current is relatively low, and it can be assumed therefor that an SCR will cease to conduct whenever a sine wave being conducted passes through its zero point.
The prior art circuit shown in copending U.S. patent application Ser. No. 719,348, filed Aug. 31, 1976 is modified herein by substituting the clock utilized in application Ser. No. 719,348 with a pulse generator coupled to a generating means in a manner to deliver a set number of clocking pulses for each electrical cycle regardless of frequency of the generator output. The adjustable clock of application Ser. No. 719,348 provides adequate adjustment to be usable with different but relatively stable frequency signals are available.
The present device makes the controller device useful for controlling power in wide frequency variations.